1. Field of the Invention
The present invention relates generally to inlet leaks for mass spectrometers, and more particularly to a method of fabricating an inlet leak for use in high pressure, hostile environments.
2. Description of the Prior Art
A number of circumstances exist in which it is necessary to provide a highly reliable inlet leak for a mass spectrometer in high pressure, highly hostile environments. Circumstances of this type exist, for example, in the field of interplanetary explorations. In particular, studies conducted on the planet Venus require inlet leaks capable of withstanding intense pressures, high temperatures, and a highly corrosive atmosphere. Other less dramatic uses for similar inlet leaks exist in numerous industrial processes wherein similar high pressure, high temperature corrosive atmospheres exist.
Previously available inlet leaks have proven unsatisfactory for use in the types of hostile environments described above. For example, conventional sintered ceramic leaks are unreliable in such environments since they can substantially modify gas constituents being measured due to gas being adsorbed on the walls of the porous ceramic material. The adsorbed species would then outgas at later times, causing substantial sample distortions. Similarly, the small openings in the porous ceramic material are susceptible to blockage, which can result in a loss of calibration of the spectrometer instrument. It is, of course, extremely important to eliminate these problems, particularly in the field of interplanetary exploration, where probes cannot be serviced and where instruments produced and flown at great expense may be caused to fail or provide inaccurate results simply because of errors produced by inlet leaks.
Similarly, conventional low temperature glass leaks cannot be used in the types of environments mentioned above, particularly where temperatures are expected to range above 475.degree. C.
Prior known gas sampling probes made of ceramic materials are disclosed in U.S. Patents such as U.S. Pat. No. 3,559,491 to Thoen, issued Feb. 2, 1971. Similarly, a conventional inlet leak formed between the intersection of two conventional glass members is disclosed in U.S. Pat. No. 3,423,304, to Leonard, issued Jan. 21, 1969. These prior art techniques exemplify some of the shortcomings in the prior art pointed out above.